Add all 23 GoF design pattern implementations (2026-06-13)

02-structural/facade/VideoConversionFacade.java

@@ -0,0 +1,39 @@
+package facade;
+
+/**
+ * Facade — the single, simple entry point to a complex video subsystem.
+ *
+ * Without this class, clients need to know about CodecFactory,
+ * BitrateReader, AudioMixer, and VideoFile — 4 classes, dozens of methods.
+ * The facade reduces that to ONE method call.
+ *
+ * The subsystem classes still exist and can be used directly
+ * by advanced users who need fine-grained control.
+ */
+public class VideoConversionFacade {
+
+    public String convertVideo(String inputFile, String targetFormat) {
+        System.out.println("VideoConversionFacade: starting conversion of " + inputFile);
+
+        // Step 1: open the file and detect codec
+        VideoFile file = new VideoFile(inputFile);
+        Codec sourceCodec = CodecFactory.extract(file);
+
+        // Step 2: prepare destination codec
+        Codec destCodec;
+        if ("mp4".equals(targetFormat)) {
+            destCodec = new MPEG4CompressionCodec();
+        } else {
+            destCodec = new OggCompressionCodec();
+        }
+
+        // Step 3: read, mix audio, encode
+        VideoFile buffer = BitrateReader.read(file, sourceCodec);
+        VideoFile intermediateResult = BitrateReader.convert(buffer, destCodec);
+        VideoFile result = AudioMixer.fix(intermediateResult);
+
+        String outputFilename = inputFile.replaceAll("\\.[^.]+$", "." + targetFormat);
+        System.out.println("VideoConversionFacade: conversion complete -> " + outputFilename);
+        return outputFilename;
+    }
+}